A device for connecting external lines to a programmable controller, which can be linked to the latter for transmitting signals and can be installed at any distance from the programmable controller, is described in German Patent Application No. 43 23 440 A1. The connecting device makes it possible to have a modular layout in which each actuator or sensor connection can be provided with one terminal, which, depending on the type of connection, can be provided with an electronic module for signal matching and conversion. Input and output modules can be mixed in any combination. This has an advantageous effect on project planning, installation, troubleshooting, and upgrading of the electronic device. The connecting device simultaneously functions as a support unit for the electronic modules, which are designed in the form of plug-in modules, and has a plurality of equidistant, adjacent receptacles of the same type for those modules. Supply and signal lines are routed to the electronic modules via a connector attached to the receptacle. Each electronic module contains a signal matching circuit for the signals of a signal channel supplied on the external lines. Connecting elements for connecting external lines are attached with the same spacing as the receptacles and are assigned to the latter.